MI5 to scrutinise operations after British PM calls for review

In the wake of the London Bridge attack after Theresa May took the unusual step of calling publicly for a review, the British domestic intelligence agency MI5 will take a hard look at its counter-terrorism operations.

May's call reflects concern over a sudden increase in the tempo of attacks and plots, The Guardian reports.

There is also a worry over whether the police and security services missed opportunities. The Italian intelligence had apparently flagged up to its British counterparts worries about the third attacker, the Moroccan-Italian Youssef Zaghba.

May pledged that MI5 would carry out a review after being repeatedly challenged about how the Home Office, police and intelligence services dealt with the information relating to the attackers.

"We need to look at how the terror threat is evolving, the way that terrorism is breeding terrorism and the increased tempo of attacks. We have had three horrific attacks and we have foiled five others. The tempo is there in a way we haven't seen before," May had said.

"We will look at how the processes were followed, what they did. They will want to be looking at that because they will want to learn lessons for the future, if there are those lessons to be learned," she added.

MI5 conducts reviews after every attack to see what lessons can be learned. At present, it is still engaged in investigations into the Manchester bombing as well as the London attacks.

Earlier in the day, it was reported that London attack ringleader Khuram Butt was identified as a major potential threat, which led to an investigation starting in 2015.

"The British police and the MI5 began investigating Butt intensively as part of a major drive to dismantle and destabilise al-Muhajiroun, a grouping of extremists in the U.K. supportive of the ISIS," U.K. counter-terrorism officials told CNN.

The investigation into Butt involved a "full package" of investigatory measures.

As soon as the British extremists began to flock to Syria to join the ISIS' newly declared caliphate in 2014, counter-terrorism officials moved more aggressively to take down al-Muhajiroun.

Butt was considered to be potentially one of the most dangerous extremists in the U.K., owing to his hardline views.

After the ISIS called for attacks in the West in September 2014, the British security services grew increasingly concerned that al-Muhajiroun members, who had remained in the U.K., would carry out terrorist attacks. One of those they were most concerned about was Butt.

The police say Butt was one of the three men, who rammed a van into pedestrians on the London Bridge before launching a stabbing spree in bars and restaurants at nearby Borough Market on Saturday night. All three were shot dead by the police.

As many as seven people were killed and 48 others were injured.